Leukapheresis is a medical procedure that removes white blood cells from a patient’s blood. It involves drawing blood, separating specific white blood cells, and returning the remaining blood components. It is a specialized form of apheresis, which is a broader term for separating any specific component from the blood and returning the rest. This technique allows for targeted intervention, either to reduce dangerously high white blood cell counts or to collect certain cells for future treatments.
The Leukapheresis Procedure
The procedure involves circulating a patient’s blood through a specialized machine. Blood is typically drawn from a vein in one arm, or sometimes through a central catheter placed in a larger vein, such as in the neck or under the collarbone. This blood then enters an apheresis machine, which uses a centrifuge to separate the blood into its various components based on their density.
Within the machine, white blood cells are collected in a separate bag. The remaining blood components, including red blood cells, plasma, and platelets, are then returned to the patient’s body through a different intravenous line, usually in the other arm or the same central catheter. The entire procedure typically takes between two and six hours, depending on the volume of blood processed and the specific cells being collected.
Therapeutic Applications for High White Blood Cell Counts
Leukapheresis serves as a rapid intervention for conditions characterized by extremely high white blood cell counts, a state known as hyperleukocytosis. Hyperleukocytosis is defined as a peripheral blood leukocyte count exceeding 100,000 cells per microliter, though in some leukemias, complications can arise at lower counts, such as 50,000 cells per microliter in acute myeloid leukemia (AML). This condition is a medical emergency due to the risk of leukostasis, where the excessive number of immature white blood cells can obstruct small blood vessels, particularly in the lungs and central nervous system.
Leukostasis can lead to severe symptoms like shortness of breath, headaches, blurred vision, dizziness, confusion, and even bleeding. While chemotherapy is the primary long-term treatment for reducing white blood cell counts, it can take several days to become effective. Leukapheresis offers an immediate reduction in circulating white blood cells, alleviating acute symptoms of leukostasis and stabilizing the patient until chemotherapy can be initiated. This procedure is commonly employed in certain types of leukemia, including acute myeloid leukemia and acute lymphoblastic leukemia, where rapid proliferation of abnormal white blood cells is a concern.
Leukapheresis for Stem Cell and Cell Therapy Collection
Beyond its immediate therapeutic use, leukapheresis is also used for collecting specific cell types for future treatments. A significant application is the collection of hematopoietic stem cells (HSCs) from peripheral blood. These immature cells can differentiate into all types of blood cells. They are collected for procedures like bone marrow transplants, which can be autologous (using the patient’s own cells) or allogeneic (using cells from a donor).
Before collection, patients or donors often receive medications to encourage the stem cells to move from the bone marrow into the peripheral bloodstream, making them more accessible for collection. Leukapheresis is also used in advanced cell therapies like CAR T-cell therapy.
T-cells, a type of white blood cell, are collected from the patient’s blood via leukapheresis. These collected T-cells are genetically modified in a laboratory to specifically target and destroy cancer cells. After modification, these CAR T-cells are reinfused into the patient to fight various hematologic malignancies.
Patient Experience and Considerations
Patients undergoing leukapheresis are made comfortable in a bed or reclining chair during the procedure. Before the process begins, medical staff will explain what to expect and may take baseline measurements such as blood pressure and heart rate. Access to the bloodstream is gained through intravenous lines.
During the procedure, patients are awake and can engage in quiet activities like reading or watching a movie. While generally painless, some individuals may experience sensations such as numbness or tingling in their hands, feet, or around the mouth. These sensations indicate a temporary drop in calcium levels, which occurs due to the anticoagulant used. Medical staff monitor calcium levels and can administer intravenous calcium to alleviate these symptoms.
Other potential side effects include temporary dizziness, fainting, or minor pain and bruising at the needle insertion sites. Following the procedure, patients are monitored for a short period and may have blood tests to check cell counts and electrolyte levels.